Evolutionary variation

The ape inside us: Chimpanzee behavior and human evolution

Rosati, A. G. (2018). The ape inside us: Chimpanzee behavior and human evolution. Natural History, 126, 34-36.

[PDF] Abstract
Darwin noted that a major challenge for his theory of human evolution was “the high standard of intellectual powers and moral disposition” that our species has obtained. Yet Darwin was also a forerunner of the nascent field of comparative psychology—gathering observations of animals from animal breeders, his own pets, and primates in the London Zoo—and ultimately made a strong argument for continuity between human and animal behavior. This tension between how animals can both appear incredibly humanlike, but also sometimes quite alien, has long captivated scientists—along with anyone who’s ever pondered what’s going on in the mind of their pet.

Chimpanzee cognition and the roots of the human mind

Rosati, A.G. (2017). Chimpanzee cognition and the roots of the human mind. In: Chimpanzees and Human Evolution (M. Muller, R. Wrangham & D. Pilbeam, eds.). Cambridge: The Belknap Press of Harvard University Press, pp. 703-745.

[PDF] Abstract
The origins of the human mind have been a puzzle ever since Darwin (1871, 1872). Despite striking continuities in the behavior of humans and nonhumans, our species also exhibits a suite of abilities that diverge from the rest of the animal kingdom: we create and utilize complex technology, pass cultural knowledge from generation to generation, and cooperate across numerous and diverse contexts. Why do humans exhibit these abilities, but other animals (mostly) do not? This is a fundamental question in biology, psychology, and philosophy. This puzzle involves two main parts. The first is concerned with identifying the psychological capacities that are unique to humans. This phylogenetic question can be addressed through careful comparisons of humans and other animals to pinpoint the cognitive traits that are likely derived in our species. The second is concerned with the function of these capacities, and the context in which they arose. This evolutionary question examines why, from an ultimate perspective, we evolved these specialized capacities in the first place. Solving these puzzles poses a special challenge because it is only possible to directly measure the cognition of living animals. The bodies of extinct species leave traces in the fossil record, and even some behavioral traits exhibit well-understood relationships with physical traits—such as relationships between dentition and dietary ecology, or mating system and sexual size dimorphism. These relationships provide important benchmarks when biologists infer the behavior of extinct species. Unfortunately, cognition does not fossilize, and neither do the brains that generate cognitive abilities. Even those features of neuroanatomy that do leave some trace in the fossil record—such as brain size or particular anatomical landmarks—are often related to the kinds of complex cognitive capacities potentially unique to humans in a coarse fashion. As such, identifying derived human cognitive traits requires reconstructing the mind of the last common ancestor of chimpanzees (Pan troglodytes), bonobos (Pan paniscus), and humans (Homo sapiens). This reconstruction then can be used to infer what cognitive characteristics have changed in the human lineage.

Ecological variation in cognition: Insights from bonobos and chimpanzees.

Rosati, A.G. (2017). Ecological variation in cognition: Insights from bonobos and chimpanzees. In: Bonobos: Unique in Mind, Brain and Behavior (B. Hare & S. Yamamoto, eds.). Oxford: Oxford University Press, pp. 157-170. 

[PDF] Abstract
Bonobos and chimpanzees are closely related, yet they exhibit important differences in their wild socio-ecology. Whereas bonobos live in environments with less seasonal variation and more access to fallback foods, chimpanzees face more competition over spatially distributed, variable resources. This chapter argues that bonobo and chimpanzee cognition show psychological signatures of their divergent wild ecology. Current evidence shows that despite strong commonalities in many cognitive domains, apes express targeted differences in specific cognitive skills critical for wild foraging behaviours. In particular, bonobos exhibit less accurate spatial memory, reduced levels of patience and greater risk aversion than do chimpanzees. These results have implications for understanding the evolution of human cognition, as studies of apes are a critical tool for modelling the last common ancestor of humans with nonhuman apes. Linking comparative cognition to species’ natural foraging behaviour can begin to address the ultimate reason for why differences in cognition emerge across species.

Tolerant Barbary macaques maintain juvenile levels of social attention in old age, but despotic rhesus macaques do not

Rosati, A. G., & Santos, L. R. (2017). Tolerant Barbary macaques maintain juvenile levels of social attention in old age, but despotic rhesus macaques do not. Animal Behaviour, 130, 199-207.

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Complex social life is thought to be a major driver of complex cognition in primates, but few studies have directly tested the relationship between a given primate species’ social system and their social cognitive skills. We experimentally compared lifespan patterns of a foundational social cognitive skill (following another’s gaze) in tolerant Barbary macaques, Macaca sylvanus, and despotic rhesus macaques, Macaca mulatta. Semi-free-ranging monkeys (N = 80 individuals from each species) followed gaze more in test trials where an actor looked up compared to control trials. However, species differed in ontogenetic trajectories: both exhibited high rates of gaze following as juveniles, but rhesus monkeys exhibited declines in social attention with age, whereas Barbary macaques did not. This pattern indicates that developmental patterns of social attention vary with social tolerance, and that diversity in social behaviour can lead to differences in social cognition across primates.

Foraging cognition: Reviving the ecological intelligence hypothesis

Rosati, A. G. (2017). Foraging cognition: Reviving the ecological intelligence hypothesis. Trends in Cognitive Sciences, 21, 691-702.

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What are the origins of intelligent behavior? The demands associated with living in complex social groups have been the favored explanation for the evolution of primate cognition in general and human cognition in particular. However, recent comparative research indicates that ecological variation can also shape cognitive abilities. I synthesize the emerging evidence that ‘foraging cognition’ – skills used to exploit food resources, including spatial memory, decision-making, and inhibitory control – varies adaptively across primates. These findings provide a new framework for the evolution of human cognition, given our species’ dependence on costly, high-value food resources. Understanding the origins of the human mind will require an integrative theory accounting for how humans are unique in both our sociality and our ecology.

Decisions under uncertainty: preferences, biases, and choice

Rosati, A. G. (2017). Decisions under uncertainty: preferences, biases, and choice. In: APA Handbook of Comparative Psychology, Volume 2. (J. Call, ed.). American Psychological Association, pp. 329-357.

[PDF]  Abstract

Imagine a choice between two potential jobs: a position that is stable but intellectually mundane, or one that is more exciting but offers only short contract with some chance of renewal. These kinds of decisions can be agonizing because they involve uncertainty. While the first job option is a known quantity, the second job offers the possibility of being more fulfilling, but also the possibility of being let go in the near future. This uncertainty means that it is not possible to know the exact consequences of the decision in advance, making it difficult to judge the best course of action. Many important decisions involve this same sort of uncertainty—such as whether to invest in a new business, commit to a partner, or pursue a medical treatment. Yet uncertainty is not something only humans experience: it is pervasive in the natural world, and all animals must sometimes make decisions without complete information about the consequences of their actions. Consequently, illuminating how decision-makers respond to uncertainty is a problem of interest across both the social and biological sciences. This review will integrate theory from economics, psychology, and biology in order to understand the psychological mechanisms that animals use to make decisions under uncertainty, as well as what biological function these mechanisms might have. I further argue that comparative research is a powerful tool for understanding the nature of economic decision-making. Discovering that a particular decision-making pattern is widely shared across humans and other species—or conversely, unique to humans alone—can provide important insights about the types of experiences that engender these psychological processes.

The evolution of primate executive function: from response control to strategic decision-making

Rosati, A. G. (2017). The evolution of primate executive function: from response control to strategic decision-making. In: Evolution of Nervous Systems, Second Edition, Volume 3 (J. Kaas & L. Krubitzer, eds.). Amsterdam: Elsevier, pp. 423-437.

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Human cognition is permeated by self-control: the ability to engage in complex, goal-oriented behaviors rather than just react to the moment at hand. This chapter examines the evolutionary roots of these abilities by comparing the psychological capacities of humans and other primates. In fact, there is marked variation in how different primate species control their motoric responses to inhibit prepotent but ineffectual actions, engage in strategic decision-making to determine the best course of action, and learn and update their responses when contingencies change. Understanding how and why this variation emerged can shed light on the origins of human cognition.

Understanding human gaze

Bettle, R., & Rosati, A. G. (2016). Understanding human gaze. In: Encyclopedia of Evolutionary Psychological Science (T. Shackelford and V. Weekes-Shackelford, eds.). Springer, pp. 1-4.

[PDF]  [Publisher’s Version]  Abstract

Social attention is a foundational component of human social behavior. Our ability to detect and think about the direction of other’s gaze involves the attribution of mental states to others and scaffolds the development of other complex cognitive skills. Gaze-following is also widespread among other primates, but the cognitive mechanisms underlying gaze-sensitive behaviors appear to differ across species. Understanding the evolutionary origins of human social attention capacities can reveal the roots of our species’ unique patterns of cognition and culture.

Uncovering the behavior and cognition of the earliest stone tool makers

Rosati, A. G. (2016). Uncovering the behavior and cognition of the earliest stone tool makers. Evolutionary Anthropology , 25, 269–270.

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In August 2016, the 13th Human Evolution Workshop at the Turkana Basin Institute (TBI) brought together a diverse group of scientists from archeology, paleontology, geology, primatology, cognition, and neuroscience. Organized by Sonia Harmand (Stony Brook and TBI), and Helene Roche (Centre National de la Recherche Scientifique) along with TBI director Lawrence Martin (Stony Brook), the workshop focused on the earliest evidence of stone knapping. This focus was spurred by the recent discovery of stone tools at the Lomekwi 3 site in Kenya, which have been dated to 3.3 Mya. It is suspected that these tools were produced by Kenyathropus platyops, the only hominin found in the region during that period. As delineated by Richard Leakey (Stony Brook and TBI), our task was to assess whether these tools represent a “cognitive Rubicon” —a fundamental transition in our lineage that demarcates the human species.

Reward type modulates human risk preferences

Rosati, A. G., & Hare, B. (2016). Reward type modulates human risk preferences. Evolution and Human Behavior, 37, 159–168.

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Money and biological rewards differ in many ways. Yet studies of human decision-making typically involve money, whereas nonhuman studies involve food. We therefore examined how context shifts human risk preferences to illuminate the evolution of decision-making. First, we assessed peoples’ risk preferences across food, prizes, and money in a task where individuals received real rewards and learned about payoffs through experience. We found that people were relatively more risk-seeking for both food and prizes compared to money—indicating that people may treat abstract reward markers differently from concrete rewards. Second, we compared human risk preferences for food with the performance of our closest phylogenetic relatives, chimpanzees (Pan troglodytes) and bonobos (Pan paniscus), in order to illuminate the evolutionary origins of human decision-making strategies. In fact, human and chimpanzees were both relatively more risk-seeking compared to bonobos. Finally, we investigated why people respond differently to money versus concrete rewards when making decisions. We found that people were more risk-prone when making decisions about money that was constrained as a store of value, compared to money that could be freely exchanged. This shows that people are sensitive to money’s usefulness as a store of value that can be used to acquire other types of rewards. Our results indicate that humans exhibit different preferences when making risky decisions about money versus food, an important consideration for comparative research. Furthermore, different psychological processes may underpin decisions about abstract rewards compared to concrete rewards.

 

Bonobos and chimpanzees exhibit human-like framing effects

Krupenye, C., Rosati, A. G., & Hare, B. (2015). Bonobos and chimpanzees exhibit human-like framing effects. Biology Letters, 11, 20140527.

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Humans exhibit framing effects when making choices, appraising decisions involving losses differently from those involving gains. To directly test for the evolutionary origin of this bias, we examined decision-making in humans’ closest living relatives: bonobos (Pan paniscus) and chimpanzees (Pan troglodytes). We presented the largest sample of non-humans to date (n = 40) with a simple task requiring minimal experience. Apes made choices between a ‘framed’ option that provided preferred food, and an alternative option that provided a constant amount of intermediately preferred food. In the gain condition, apes experienced a positive ‘gain’ event in which the framed option was initially presented as one piece of food but sometimes was augmented to two. In the loss condition, apes experienced a negative ‘loss’ event in which they initially saw two pieces but sometimes received only one. Both conditions provided equal pay-offs, but apes chose the framed option more often in the positive ‘gain’ frame. Moreover, male apes were more susceptible to framing than were females. These results suggest that some human economic biases are shared through common descent with other apes and highlight the importance of comparative work in understanding the origins of individual differences in human choice.

 

The evolutionary roots of human decision-making

Santos, L. R., & Rosati, A. G. (2015). The evolutionary roots of human decision-making. Annual Review of Psychology, 66, 321-347.

[PDF]  [Publisher’s Version]  Abstract

Humans exhibit a suite of biases when making economic decisions. We review recent research on the origins of human decision making by examining whether similar choice biases are seen in nonhuman primates, our closest phylogenetic relatives. We propose that comparative studies can provide insight into four major questions about the nature of human choice biases that cannot be addressed by studies of our species alone. First, research with other primates can address the evolution of human choice biases and identify shared versus human-unique tendencies in decision making. Second, primate studies can constrain hypotheses about the psychological mechanisms underlying such biases. Third, comparisons of closely related species can identify when distinct mechanisms underlie related biases by examining evolutionary dissociations in choice strategies. Finally, comparative work can provide insight into the biological rationality of economically irrational preferences.

 

Comparative developmental psychology: How is human cognitive development unique?

Rosati, A. G., Wobber, V., Hughes, K., & Santos, L. R. (2014). Comparative developmental psychology: How is human cognitive development unique?. Evolutionary Psychology, 12, 448-473.

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The fields of developmental and comparative psychology both seek to illuminate the roots of adult cognitive systems. Developmental studies target the emergence of adult cognitive systems over ontogenetic time, whereas comparative studies investigate the origins of human cognition in our evolutionary history. Despite the long tradition of research in both of these areas, little work has examined the intersection of the two: the study of cognitive development in a comparative perspective. In the current article, we review recent work using this comparative developmental approach to study non-human primate cognition. We argue that comparative data on the pace and pattern of cognitive development across species can address major theoretical questions in both psychology and biology. In particular, such integrative research will allow stronger biological inferences about the function of developmental change, and will be critical in addressing how humans come to acquire species-unique cognitive abilities.

The ecology of spatial memory in four lemur species

Rosati, A. G., Rodriguez, K., & Hare, B. (2014). The ecology of spatial memory in four lemur species. Animal Cognition, 17, 947-961.

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Evolutionary theories suggest that ecology is a major factor shaping cognition in primates. However, there have been few systematic tests of spatial memory abilities involving multiple primate species. Here, we examine spatial memory skills in four strepsirrhine primates that vary in level of frugivory: ruffed lemurs (Varecia sp.), ring-tailed lemurs (Lemur catta), mongoose lemurs (Eulemur mongoz), and Coquerel’s sifakas (Propithecus coquereli). We compare these species across three studies targeting different aspects of spatial memory: recall after a long-delay, learning mechanisms supporting memory and recall of multiple locations in a complex environment. We find that ruffed lemurs, the most frugivorous species, consistently showed more robust spatial memory than the other species across tasks—especially in comparison with sifakas, the most folivorous species. We discuss these results in terms of the importance of considering both ecological and social factors as complementary explanations for the evolution of primate cognitive skills.

Chimpanzees and bonobos exhibit emotional reactions to decision outcomes

Rosati, A. G., & Hare, B. (2013). Chimpanzees and bonobos exhibit emotional reactions to decision outcomes. PLoS One, 8 e63058.

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The interface between cognition, emotion, and motivation is thought to be of central importance in understanding complex cognitive functions such as decision-making and executive control in humans. Although nonhuman apes have complex repertoires of emotional expression, little is known about the role of affective processes in ape decision-making. To illuminate the evolutionary origins of human-like patterns of choice, we investigated decision-making in humans’ closest phylogenetic relatives, chimpanzees (Pan troglodytes) and bonobos (Pan paniscus). In two studies, we examined these species’ temporal and risk preferences, and assessed whether apes show emotional and motivational responses in decision making contexts. We find that (1) chimpanzees are more patient and more risk-prone than are bonobos, (2) both species exhibit affective and motivational responses following the outcomes of their decisions, and (3) some emotional and motivational responses map onto species-level and individual-differences in decision-making. These results indicate that apes do exhibit emotional responses to decision-making, like humans. We explore the hypothesis that affective and motivational biases may underlie the psychological mechanisms supporting value-based preferences in these species.